Image Forming Apparatus

The present application claims priority from Japanese Application JP2024-092428, the content to which is hereby incorporated by reference in to this publication.

This disclosure relates to an image forming apparatus, and more particularly, to an image forming apparatus including an optical scanning device that scans a photoreceptor with multiple beams emitted from a plurality of laser light sources.

Conventionally, in an image forming apparatus, an interleave scanning method has been adopted as means to achieve pseudo high-resolution in a sub-scanning direction. In the interleave scanning method, when a laser beam is physically scanned at a real latent-image line position, an electrostatic latent image is formed at a virtual latent-image line position without physically scanning the laser beam at the virtual latent-image line position between two pieces of real latent-image line positions.

In addition, by adjusting a light amount (intensity or irradiation time) of the laser beam at the real latent-image line position, a toner image can be made to be developed at the virtual latent-image line position without developing the toner image at the real latent-image line position.

However, when gradation expression is performed by an area gradation method, an image pattern expressing each gradation level is formed by various dot patterns and thus, even when density adjustment is performed with a line image, there was a possibility that an accurate density (accurate gradation level) cannot be acquired depending on the dot pattern.

In order to solve the problem as above, there has been proposed an image forming apparatus of an interleave scanning method in which an image pattern including both dots at real latent-image line positions and dots at virtual latent-image line positions is formed in a reference image pattern for adjustment of light intensity or irradiation time, and density adjustment is performed.

In addition, due to face tangle error of a polygon mirror in an exposure device, periodic jitter may occur in a scanning position of the laser beam, and a pitch between the scanning positions may vary. When the pitch between the scanning positions varies, density unevenness or color shift in the sub-scanning direction occurs.

In order to solve the problem as above, there has been proposed an image forming apparatus of an interleave scanning type in which a light amount correction value is varied in accordance with a pitch.

Incidentally, in an image forming apparatus using multiple beams, a phenomenon called reciprocal law failure in which a region across scanning becomes dense is known. However, since an art of the conventional image forming apparatus of the interleave scanning method does not take the reciprocal law failure into consideration, there is a possibility that the dot formation in the region across scanning of the polygon mirror becomes thicker and denser as compared with the dot formation not in the region across scanning.

This disclosure was made in view of the circumstances as described above, and an object of this disclosure is to provide an image forming apparatus that is less likely to be affected by reciprocal law failure than before when pseudo high-resolution processing is executed in the sub-scanning direction.

This disclosure is to provide an image forming apparatus characterized by including: an image-data acquirer that acquires image data; a photoreceptor; a charger that charges the photoreceptor; an exposure section that forms an electrostatic latent image on the photoreceptor in a charged state; a developer that supplies a toner to the photoreceptor and forms a toner image corresponding to the electrostatic latent image; a transferer that transfers the toner image to a print sheet; an image former including a fixer that heats and fixes the toner image to the print sheet; and one or more controllers that control the image-data acquirer, the photoreceptor, the charger, the exposure section, the developer, the transferer and the image former, the exposure section including: a plurality of laser light-sources that emit a plurality of laser beams; a polygon mirror that deflects the plurality of laser beams by a plurality of mirror surfaces and emits the same to a scanning region of the photoreceptor; a laser driver that forms the electrostatic latent image by irradiating the scanning region of the photoreceptor in the charged state with the plurality of laser beams on the basis of the image data acquired by the image-data acquirer; and a laser corrector that corrects the laser beam, in which the one or more controllers control the exposure section to form a real latent-image line by irradiating the scanning region of the photoreceptor with the plurality of laser beams in a main-scanning direction, determines whether or not a virtual latent-image line is formed between two pieces of the real latent-image lines adjacent to each other in a sub-scanning direction, and causes the laser corrector to correct the plurality of laser beams and adjusts density of the virtual latent-image line on the basis of the determination result.

According to this disclosure, when the pseudo high-resolution processing in the sub-scanning direction is to be executed, an image forming apparatus, which is less likely to be affected by reciprocal law failure than before can be realized by determining whether or not a virtual latent-image line is formed between two real latent-image lines adjacent to each other in the sub-scanning direction and by adjusting the density of the virtual latent-image line by causing the laser corrector to correct the plurality of laser beams on the basis of the determination result.

In this disclosure, an “image forming apparatus” is, for example, an apparatus that forms and outputs an image, such as a copying machine having a copying (copy) function, including a printer that uses an electrophotographic format for image formation with a toner, or a Multifunction Peripheral (MFP) that includes also functions other than copying.

The “image-data acquirer” of this disclosure is realized by an image readerin Embodiment 1, which will be described later.

In addition, the “photoreceptor” of this disclosure is realized by a photosensitive drum.

In addition, a “charger” of this disclosure is realized by a charger.

In addition, an “exposure section” of this disclosure is realized by an optical scanning device.

In addition, a “developer” of this disclosure is realized by a developing device.

In addition, a “transferer” of this disclosure is realized by an intermediate transfer belt.

Furthermore, preferred embodiments of this disclosure will be explained.

In the image forming apparatus according to this disclosure, when a virtual latent-image line is formed, the one or more controllers may determine whether or not the virtual latent-image line is formed in a region across scanning between a scanning region of the photoreceptor by the mirror surface of the polygon mirror and a scanning region of the photoreceptor by the subsequent mirror surface, and when the virtual latent-image line is formed in the region across scanning, the one or more controllers may cause the laser corrector to correct the plurality of laser beams so as to lower the density of the virtual latent-image line than the case where the virtual latent-image line is formed without changing the mirror surface of the polygon mirror.

As described above, when the pseudo high-resolution processing in the sub-scanning direction is to be executed, in a case where the virtual latent-image line is formed, it is determined whether or not the virtual latent-image line is formed in the region across scanning between the scanning region of the photoreceptor by one mirror surface of the polygon mirror and the scanning region of the photoreceptor by the subsequent mirror surface. And when the virtual latent-image line is formed in the region across scanning, the laser corrector is caused to correct the plurality of laser beams so that the density of the virtual latent-image line is made lower than the case where the virtual latent-image line is formed without changing the mirror surface of the polygon mirror. In this way, it is possible to realize an image forming apparatus that is less likely to be affected by reciprocal law failure than before.

In the image forming apparatus according to this disclosure, when the virtual latent-image line is formed in the region across scanning, the one or more controllers may determine whether or not the real latent-image line is formed at a real latent-image position adjacent to the virtual latent-image line, and when the real latent-image line is formed at the real latent-image position, the laser corrector may be caused to correct the plurality of laser beams such that the density of the virtual latent-image line is made lower than the case where the real latent-image line is not formed at the real latent-image position.

As described above, in a case where the virtual latent-image line is formed in the region across scanning, it is determined whether or not the real latent-image line is formed at the real latent-image position adjacent to the virtual latent-image line. And when the real latent-image line is formed at the real latent-image position, the laser corrector is caused to correct the plurality of laser beams so that the density of the virtual latent-image line is made lower than the case where the real latent-image line is not formed at the real latent-image position. In this way, it is possible to realize an image forming apparatus that is less likely to be affected by reciprocal law failure than before.

In the image forming apparatus according to this disclosure, the laser corrector may adjust the density of the virtual latent-image line by correcting at least one of a PWM DUTY ratio of the plurality of laser beams, bias currents of the plurality of laser light sources, and light amounts of the plurality of laser beams.

As described above, when the pseudo high-resolution processing in the sub-scanning direction is to be executed, it is determined whether or not a virtual latent-image line is formed between two pieces of the real latent-image lines adjacent to each other in the sub-scanning direction. And on the basis of the determination result, the laser corrector is caused to correct the PWM DUTY ratios of the plurality of laser beams, the bias currents of the plurality of laser light sources, and the laser-beam amounts of the plurality of laser beams so as to appropriately adjust the density of the virtual latent-image line. In this way, it is possible to realize an image forming apparatus that is less likely to be affected by reciprocal law failure than before.

Hereinafter, this disclosure will be described in more detail with reference to the drawings. Note that the following explanation is exemplification in all respects and should not be construed as limiting this disclosure.

A schematic configuration of a digital multifunction machinethat is one embodiment of an image reader of this disclosure will be explained on the basis of.

is a perspective view illustrating an appearance of the digital multifunction machineaccording to Embodiment 1 of this disclosure.

is a sectional diagram illustrating a mechanism configuration of a main body of the digital multifunction machineillustrated in.

The digital multifunction machineis an apparatus such as a multifunction machine or an MFP, which digitally processes image data and has a copying function, a scanner function, and a facsimile function.

The digital multifunction machineexecutes jobs of scanning, printing, and copying on the basis of an instruction from a user received via an operation acceptoror a communicator.

Here, an internal configuration of the digital multifunction machineshown inwill be explained in brief.

The digital multifunction machineprints a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y) on a print sheet.

Thus, as the internal configuration of the digital multifunction machine, four each of developing devices, photosensitive drums, drum cleaning devices, chargersand the like are provided.

In order to form four types of toner images corresponding to the respective colors, four image stations Pa, Pb, Pc, and Pd are constituted in the digital multifunction machinecorrespondingly to black, cyan, magenta, and yellow, respectively.

Note that the digital multifunction machinemay print a monochrome image using a single color (black, for example) on a print sheet.

In each of the image stations Pa, Pb, Pc, and Pd, a toner image is formed as follows.

The drum cleaning deviceremoves and collects residual toner on the surface of the photosensitive drum.

Thereafter, the chargeruniformly charges the surface of the photosensitive drumto a predetermined potential.

Subsequently, the optical scanning deviceexposes the uniformly-charged surface and forms an electrostatic latent image on the surface.

Thereafter, the developing devicedevelops the electrostatic latent image.

In this way, the toner image in each color is formed on the surface of the respective photosensitive drum.

In addition, the intermediate transfer beltcircularly moves in an arrow direction AD.

The toner image in each color on the surface of each of the photosensitive drumsis sequentially transferred and superimposed onto the intermediate transfer belt, and the color toner image is formed on the intermediate transfer belt.

A belt cleaning deviceremoves and collects the residual toner on the circularly moving intermediate transfer belt.

The print sheet is picked up from one of four feed traysby a pickup rollerand is fed to a secondary transfer devicevia a sheet conveyance path R.

Alternatively, the print sheet is fed from a manual feed trayby the pickup roller, not shown, and is fed to the secondary transfer devicevia the sheet conveyance path R.

A resist rollerthat temporarily stops the print sheet and aligns leading edges of the print sheets is disposed in the sheet conveyance path R.

In addition, a conveyance rollerthat promotes conveyance of the print sheet and the like are disposed.